Electric power producing system using molten carbonate type fuel cell

ABSTRACT

A fuel gas reformed in a reformer is fed to the anode electrode of a molten carbonate type fuel cell and is used for electrochemical reaction therein, the gas discharged from the anode electrode is introduced into a carbon dioxide separator containing an carbon dioxide absorptive liquid to remove carbon dioxide gas from the exhaust gas, the separated carbon dioxide gas is fed to the cathode electrode of the fuel cell together with air, and the exhaust gas from which carbon dioxide gas has been removed is recirculated to the anode electrode of the fuel cell via the reformer.

This is a divisional of copending application(s) Ser. No. 07/424,134filed on 10/19/89.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a method of producing electric powerwith molten carbonate type fuel cell which directry converts chemicalenergy of fuel to electrical energy, and to an apparatatus for carryingout the method.

2. Background Art

A molten carbonate type fuel cell device is well known in the art. Thisparticular fuel cell device is composed of a plurality of fuel cellsstacked one after another with separators being inserted between twoadjacent fuel cells. Each fuel cell comprises a tile (electrolyte plate)of a porous substance filled with an electrolyte of a molten carbonate,which tile is sandwiched between a cathode electrode (oxygen plate) andan anode electrode (fuel plate), and an oxidizing gas is fed into thecathode electrode while a fuel gas is supplied into the anode electrodeso as to cause a reaction between the cathode and the anode and toproduce electric power.

In a case where a hydrocarbon or methanol is employed as a fuel in theelectric power-producing system using the molten carbonate type fuelcell, first the fuel gas is reformed to a fuel gas and then fed into theanode of the fuel cell.

As the means of reforming the above-mentioned fuel, an externalreformation type and an internal reformation type are popular in theart.

As the conventional external reformation type, one typical system isshown in FIG. 9 of the accompanying drawings, in which a hydrocarbon(natural gas such as methane) that is used as the fuel gas to be fedinto the anode b of the fuel cell a is first introduced into thereformer d, and then the hydrogen (H₂) and carbon monoxide (CO) formedtherein are introduced into the anode b as the fuel gas and arepartially consumed for producing electric power. On the other hand, theanode exhaust gas expelled from the anode b, as containing thenon-reacted methane (CH₄), hydrogen (H₂) and carbon monoxide (CO) inaddition to the carbon dioxide (CO₂) and water (H₂ O) generated in thefuel cell 1, is supplied into the combustion chamber of the reformer dthrough a line e and is combusted therein to product a heat necessaryfor reformation of the fuel gas. The CO₂ -containing gas exhausted fromthe combustion chamber of the reformer d passes through a line f to becombined with air A and is fed to the cathode c to be utilized for thecell reaction.

On the other hand, one typical system of the conventional internalreformation type is shown in FIG. 10, in which the reformer d is builtin the fuel cell a so that the heat from the fuel cell a is directlyutilized for the reforming reaction in the reformer d, the anode exhaustgas to be discharged from the anode b is composed of the same componentsas those constituting the anode exhaust gas in the case of theabove-mentioned external reformation type system and contains thenon-reacted CH₄, H₂ and CO. The hydrogen (H₂) is separated from theanode exhaust gas in a hydrogen-separator g and is recirculated to thereformer d thorugh a line h via a fuel feed line i to the reformer dwhile the remaining CH₄, CO and the non-separated H₂ are combusted in acatalyst combusting device j and are fed into the cathode c togetherwith the air A through a line k (U.S. Pat. No. 4,532,192).

However, in both these external reformation type and internalreformation type systems, the non-reformed CH₄ contained in the gasexhausted from the anode b and CO and H₂ not reacted in the fuel cellare combusted and then fed into the cathode c together with the air.Therefore, these systems have a drawback that the CH₄, CO and H₂ can notbe completely utilized in the cell reaction but are combusted to beconverted into a heat energy. Hence, the power-producing efficiencty ispoor. In addition, the methane (CH₄) which is not reformed in thereformer d would cause a deterioration of the power-producingefficiency. Such a deterioration has to be counterbalanced by a certainmeasure. For this purpose, generally an amount of the steam forreformation is increased and the reaction temperature for reformation iselevated. Still another problem is that the H₂ and CO not used in thefuel cell would also cause a depression of the power-producingefficiency. If the utilization factor of those gases is raised, the cellpotential would drop, and therefore, a part of these H2, and CO areinevitable to remain as they are not used. Moreover, there is stillanother problem that the non-combusted gas from the fuel cell containscarbon dioxide gas which is a low caloric gas. Therefore, an expensivecatalyst combustion device is necessary for combusting the gases.

SUMMARY OF THE INVENTION

One object of the present invention is to improve the power-producingefficiency of a fuel cell, in which the anode exhaust gas as exhaustedfrom the anode electrode of the cell is introduced into the reformer,after carbon dioxide gas has been removed from the exhaust gas, and thenrecirculated into the anode of the fuel cell.

Another object of the present invention is to provide a system of a fuelcell, in which the carbon dioxide gas as removed from the anode exhaustgas is fed into the cathode together with air.

According to one aspect of the present invention, there is provided amethod of producing electric power with a molten carbonate type fuelcell wherein an anode gas is fed into the anode chamber of the fuel celland a cathode gas into the cathode chamber thereof, which comprises thesteps of:

separating carbon dioxide gas from the anode exhaust gas as exhaustedfrom the anode chamber;

recirculating the anode exhaust gas, from which carbon dioxide gas hasbeen removed in the above step, into the anode chamber as an anode gas;and

feeding the carbon dioxide gas as separated from the anode exhaust gasinto the cathode chanber as a cathode gas.

In accordance with the present invention, there is also provided anelectrical energy producing apparatus comprising:

a plurality of molten carbonate type fuel cells, each fuel cellincluding a molten carbonate-containging electrolyte tile sandwichedbetween an anode electrode and a cathode electrode both of whichelectrodes being respectively provided with an anode chamber and acathode chamber for feeding an anode gas and a cathode gas thereto;

an anode gas feed line and an anode exhaust gas line connected with theinlet and outlet of the anode chamber of the fuel cell for feeding andexhausting the anode gas thereinto and therefrom respectively;

a cathode gas feed line and a cathode exhaust line connected with theinlet and the outlet of the cathode chamber of the fuel cell for feedingand discharging the cathode gas thereinto and therefrom, respectively;

means for feeding a fuel gas and a steam into the anode gas feed line;

a reformer for reforming the fuel gas with a steam, as connected withthe anode gas feed line;

a carbon dioxide gas separator for removing carbon dioxide gas from theanode exhaust gas in the anode exhaust gas line;

a circtulation line for recirculating into the reformer the anodeexhaust gas from which carbon dioxide gas has been removed in the carbondioxide gas separator; and

means for feeding into the cathode gas feed line the carbon dioxide gasas separated in the carbon dioxide separator.

In this system, the carbon dioxide gas separator may have a carbondioxide gas absorber, which includes a solution containing alkali saltor amine as a carbon dioxide gas absorptive liquid, and an absorbedliquid regenerator.

In the system, the fuel gas as reformed in the reformer is fed into theanode of the molten carbonate type fuel cell and is used forelectrochemical reaction. The anode exhaust gas exhausted from the anodeelectrode is introduced into the carbon dioxide separator in which thecarbon dioxide is separatred from the exhaust gas. The thus separatedcarbon dioxide gas is fed into the cathode of the fuel cell togetherwith air, whereas the anode exhaust gas from which carbon dioxide gashas been removed is recirculated to the fuel cell via the reformer. Thereformer may be either such that almost all the anode exhaust gas isintroduced thereinto so as to heat the reforming part or such that thecathode exhaust gas of the fuel cell is introduced thereinto to give theheat necessary for reformation. That is, the reformer may be either sucha type having no combustion chamber or a type having a combustionchamber. Furthermore, the reformer may be a type integrally provided tothe fuel cell, i.e., the reformer used in the internal reformation tyepfuel cell. Provision of a shift reactor in the carbon dioxide separatorin the course of the line for intoroducing the anode exhasut gasthereinto is preferred in order to facilitate the separation of carbondioxide gas in the separator. Further, it is also preferred to providemeans for combusting a part of the anode exhaust gas from the carbondioxide separator in the cumbustion device and thereafter introducingthe gas into the cathode of the fuel cell, since the temperature of thecathode may be elevated.

The anode exhaust gas discharged from the anode electrode containscarbon dioxide gas and water generated in the fuel cell, in addition tothe non-used fuel, hydrogen and carbon monoxide. However, since almostall the carbon dioxide gas is separated from the exhaust gas and is fedinto the cathode togther with air and since the anode exhaust gas fromwhich carbon dioxide gas has been removed is recirctlated to the anodevia the reformer, the fuel which is not used in the fuel cell can becompletely and effectively consumed and therefore the power-generatingefficiency is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a systematic diagram showing one embodiment of the electricpower-producing molten carbonate type fuel cell system of the presentinvention;

FIG. 2 is a schematic view of the reformer as used in FIG. 1;

FIG. 3 and FIG. 4 are system diagrams of other embodiments according tothe present invention respectively;

FIG. 5, FIG. 6 and FIG. 7 are outline views to show other types of thereformer applicable to the present invention respectively;

FIG. 8 is a system diagram illustrating one embodiment of the electricpower-producing molten carbonate type fuel cell device of the presentinvention, which employs the reformer shown in FIG. 7;

FIG. 9 is a schematic diagram showing a conventional externalreformation type electric power-producing fuel cell system; and

FIG. 10 is a schematic diagram showing a conventional internalreformation type electric power-producing fuel cell system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, preferred embodiments of the present invention will be explainedwith reference to the attached drawings.

In FIG. 1, numeral 1 designates a molten carbonate type fuel cell inwhich a molten carbonate-inpregnated tile 2 is sandwiched by an anodeelectrode 3a and a cathode electrode 4a. Both plates 3a and 4a have ananode chamber 3 and a cathode chamber 4 respectively. Numeral 5designates a reformer in which the anode exhaust gas releases a heatnecessasry for reformation and the fuel gas is thereby reformed to ananode gas. The reformer 5 is, as shown in FIG. 2, filled with reformingcatalyst 5a, and the above-mentioned exhaust gas releases a heatsufficient to maintain the reforming reaction. Numeral 6 denotes aheater provided in the course of a feed line 7 for fuel gas and steam.Numeral 8 is a line for feeding the anode gas reformed in the reformer 5to the anode chamber 3. Numeral 9 designates an anode exhaust gas lineextending from the anode chamber 3. Numeral 10 is an anode exhaust gasbranch line which is branched from the anode gas line 9 so as tointroduce the anode exhaust gas to the inlet of reformer 5 thereby toimpart the necessary heat hereto. Numeral 11 is a cooler provideddownstream of the connected point of the branch line 10 with the anodeexhaust gas line 9. Numeral 12 is a condenser provided in the anodeexhaust gas line 9 downstream of the cooler 11. Numeral 13 is a carbondioxide gas separator. The carbon dioxide gas separator 13 is, as oneexample, composed of an abosorption column 13a for absorbing carbondioxide by a carbon dioxide gas absorber, a regeneration column 13b forregenerating the aqueous diethanolamine, an aqueous amine solution feedline 13c for feeding the aqueous diethanolamine solution to theregeneration column 13b, and an aqueous amine solution recirculatingline 13d for recirculating to the absorption column 13a the aqueousdiethanolamine solution as regenerated in the regeneration column 13b.The carbon dioxide gas absorber may be an aquenous diethanolaminesolution, aqueous alkali salt solution such as potassium carbonate or amixture of such solutions.

Numeral 14 is a circulation gas line for recirculating the remaininggases such as methane and hydrogen, which are taken out from theabsorption column 13c after carbon dioxide gas has been removed in thecarbon dioxide separator 13, to the upstream of the heater 6 as providedin the fuel and steam feed line 7. Numeral 15 is a gas heater asprovided in the course of the circulation gas line 14. Numeral 16 is anair feed duct as connected to the bottom of the regeneration column 13bof the carbon dioxide gas separator 13. Numeral 17 is an air feed linefor taking out from the regeneration column 13b the carbon dioxidegas-containging air as separated in carbon dioxide gas separator 13 andfeeding the same to the cathode chamber 4 of the fuel cell 1. Numeral 18is an air heater as provided in the course of the carbon dioxide gasfeed line 17. Numeral 19 is a water-treating boiler. Numeral 20 is aline for conveying the water from the condenser 12 to the water-treatingboiler 19. Numeral 21 is a steam feed line for conveying the steam asseparated in the water-treating boiler 19 and over-heated in a heater toan over-heated steam to an upper stream part of the fuel feed line 7.Numeral 23 is an exhaust line for discharging any excessive water out ofthe system. Numeral 24 is a cathode exhaust gas line for the gasexhausted from the cathode chamber 4 of the fuel cell 1.

In one example to discribed hereunder, methane is employed as thehydrocarbon or alcohol-containing fuel gas to be fed into the fuel feedline 7. Methane is pre-heated in the heater 6 and then reformed in thereformer 5 to give hydrogen gas. Carbon monoxide gas and methane in thereformer 5 is obtained from the gas as exhausted from the anode chamber3 in this example. The anode gas reformed in the reformer 5 isintroduced into the anode chamber 3 of the fuel cell 1 via the feed line8 and is utilized for electro-chemical reaction therein. The gas to beexhuasted from the anode chamber 3 contains carbon dioxide gas (CO₂) andwater (H₂ O) which are generated in the fuel cell, in addition to thenon-used methane (CH₄), hydrogen (H₂) and carbon monoxide (CO). Most ofthese gases are transported to the reformer 5 via the anode exhaust gasbranch line 10 branched from the anode exhaust gas line 9 while a partof the same is led to the cooler 11 and the condenser 12 via the anodeexhaust gas line 9 whereupon the gas fraction is introduced into theabsorber 13a of the carbon dioxide gas separator 13. Most of the carbondioxide gas among the gas fraction transmitted into the absorber 13a isabsorbed in the aqueous diethanolamine solution as being brought intocontact therewith in the absorber 13a and is thereby removed, while thegases remaining after separation of the carbon dioxide gas which containmethane, a trace amount of carbone dioxide and hydrogen are taken outfrom the top of the absorber 13a through the residual gas line 14,pre-heated in the circulation gas heater 15, transported to the upperstream of the heater 6, reformed to an anode gas in the reformer 5 andthereafter transported to the anode chamber 3 of the fuel cell 1 inwhich the gas undergoes the cell reaction. Accordingly, the electricpower producing efficiency is raised. The aqueous amine solution whichhas absorbed the carbon dioxide gas in the absorption column 13a is fedto the regeneration column 13b via the aqueous amine solution feed lien13c, in which the carbon dioxide gas is stripped with the air suppliedfrom the air feed duct 16 and the aqueous amine solution from which thecarbone dioxide gas has been removed is recirculated to the absorptioncolumn 13a via the aqueous amine solution rcirculation line 13d and isused therein for absorbing carbon dioxide gas. The air which hascontained carbon dioxide gas in the regeneration column 13b is preheatedin the air preheater 18 and then supplied into the cathode chamber 4 ofthe fuel cell 1, in which the oxygen gas and carbon dioxide gas areutilized for electrochemical reaction.

The water separated in the condenser 12 is transported to thewater-treating boiler 19 via the line 20 whereas the steam is heated toa steam by the heater 22 in the steam feed line 21 and introduced intothe fuel feed line 7 to be utilized in the reformer 5 as a reformingsteam. The excessive water in the water treating boiler 19 is expelledout of the system via the discharge line 23.

In accordance with the present invention, as mentioned above, since thenon-used methane and hydrogen contained in the anode exhaust gas takenout through the anod exhaust gas line 9 are recovered by the carbondioxide gas separator 13 and is recirculated into the fuel cell 1 viathe reformer 5 to be utilized for the electrochemical reaction therein,the power producing efficiency may be noticeably improved as comparedwith the conventional system in which the non-used gases are effectivelynot utilized in the cell reaction but are merely combusted. In thiscase, it is satisfactory that the methane-reforming efficency in thereformer 5 be low since the methane can be recycled. Accordingly, theheat from the cell may be easily utilized as the heat necessary for thereformation reaction.

FIG. 3 shows another embodiment of the present invention. In thisparticular embodiment, a shift reactor 25 is provided between the cooler11 and the condenser 12. The other constitution is substantially same asthat of FIG. 1.

The anode exhaust gas expelled through the anode exhaust gas line 9contains, as mentioned above, H₂, CO, CO₂ and H₂ O. CO and H₂ O amongthese gases are shift-reacted to H₂ and CO₂ in the shift reactor 25,while CO₂ is separated in the carbon dioxide gas separator 13 and H₂ isrecirculated to the anode chamber 3 via the reformer 5 in the system ofFIG. 3. Accordingly, the removal of the carbon dioxide gas is easilydone, and the partial pressure of CO is lowered in the recirculationline.

FIG. 4 shows still another embodiment of the present invention. A partof the residual gases taken out from the absorption column 13a, whichinclude methane and hydrogen, is branched from the residual gas branchline 26, and introduced into and burned in the combustion device 27provided in the course of the air feed line 17. The resulting combustiongas is transported into the cathode chamber 4. This embodiment hasvarious advantages that the temperature of the cathode gas is elevatedand the power-producing efficiency is thereby improved, and accumulationof trace components which would be caused by circulation of the anodegas for a long period of time is prevented.

The system illustrated in FIG. 4 is such that the exahust gas from theanode chamber 3 is circulated to the reformer 5 via the anone exhaustgas branch line 10 extending from the anode exhaust gas line 9, in whichthe heat from the anode exhaust gas is utilized for the reformationreaction. According to the experiments by the present inventor where theflow amount of the gas to be circulated to the reformer 5 via the anodeexhaust gas branch line 10 was made three times as much as that of thegas to be transported to the carbon dioxide gas separator 13 through theanode exhaust gas line 9, and the anode outlet temperature was 700degrees C. (°C.) and the temperature in the fuel feed line 7 was 550°C., the outlet temperature of the reformer 5 was 607° C. and thereformed percentage of methane was 25.7%. Accordingly, even though thereformed percentage of methane is small, the power-producing efficiencyis high in the method of the present invention since all thenon-reformed methane is recirculated to the reformer and is utilized forthe cell reaction.

Only the carbon dioxide gas is removed from the gases introduced intothe carbon dioxide gas separator 13 through the anode exhaust gas line9. Here, when an aqueous 30 wt. % diethanolamine solution is employed asa solution for absorbing the carbon dioxide gas, 85.8% of the carbondioxide gas in the anode exhaust gas may be absorbed or removed in theabsorption column 13a. The remaining gases thus separated includemethane, hydrogen, carbon monoxide, carbon dioxide and water and thosegases are entirely recirculated to the reformer 5. Therefore, there isno fuel loss. When an air which corresponds to the oxygen utilizationpercentage of 50% is utilized as the stripping gas in the regeneratorcolumn 13b, all the carbon dioxide gas absorbed in the absorption column13a can be stripped and transported to the cathode 4 together with air.Accordingly, any additional heat, for example by steam, is unnecessaryfor regeneration.

Next, the 200 KW-grade power-producing fuel cell system which is drivenunder normal pressure and which has the constitution shown in FIG. 1 wascompared with the conventional external reformation type fuel cell, andthe results are as shown in the Table below.

    ______________________________________                                                     Conventional                                                                  External  System of                                                           Reformation                                                                             the Invention of                                                    Type Fuel Cell                                                                          FIG. 1                                                 ______________________________________                                        Current Density of Cell                                                                      150         150                                                (mA/cm.sup.2)                                                                 Volate (mV/cell)                                                                             712         750                                                Number of cells                                                                              323         307                                                Power Producing Capacity                                                                     230         230                                                (kW)                                                                          Amount of Metane Used                                                                        1.91        1.50                                               (kg*mol/hour)                                                                 ______________________________________                                    

As is obvious from the data shown in this Table, the power-producingefficiency of the system of the present invention in comparison with theconventional system is 1.91/1.5=1.27, i.e., 27% higher than that of theconventional power generation system.

FIGS. 5 through 7 show still other embodiments of the reformer of thepresent invention.

FIG. 5 shows a modified reformer 28, and the cathode exhaust gas fromthe line 24 is introduced into the heating part 28b of the reformer 28in order that the heat necessary for reformation in the reforming part28a may be obtained from the gas as taken out from the cathode chamber4, whereas the gas which has given the heat to the reformation reactionis then transported to the cathode chamber.

FIG. 6 shows another reformer 29. In this case, the heat necessary forreformation in the reforming part 29a of the reformer 29 is obtainedfrom a combustion in the combustion part 29b, and for this, a part ofthe anode exhaust gas is introduced into the combustion part 29b as acombustion gas while a part of the air to be supplied to the cathode isintroduced into the combustion part 29b via the line 29c, whereupon thegas which has given the heat for the reformation reaction is then fedinto the cathode.

FIG. 7 shows the internal reformation type fuel cell 30, in which theelectrolyte tile 2 is sandwiched between the anode electrode 3a and thecathode electrode 4a, a plurality of anode/tile/cathode units arestacked via separator plates 31 with the reformer 32 being inserted inan arbitrary separator plate 31. Each separator plate 31 defines theanode chamber 3 on one face thereof and the cathode chamber 4 on theother face thereof. The anode gas reformed in the reformer 32 issupplied into the anode chambers 3 through the line 8 formed inside thefuel cell, and the anode exhaust gas from the respective chambers 3 arecollected and discharged through the exhaust gas line 9. The cathode gascoming from the line 17 is distributed into the respective cathodechambers 4 and then flows into the line 24.

In the internal reformation type fuel cell 30, the reformation reactiontemperature is maintained by the heat derived from the anode gas in theanode chamber 3 contacting the reformer 32 and the heat derived from thecathode gas in the cathode chamber 4 which also contacts the reformer32. FIG. 8 shows an electric power-producing apparatus which employs theinternal reformation type fuel cell 30 of FIG. 7. The power-generationapparatus of FIG. 8 is same as that of FIG. 1, except that the reformeris located in the fuel cell in FIG. 8.

In the case of the conventional internal reformation type reformer asshown in FIG. 10, it is necessary that the reforming part is directlyprovided inside the anode chamber, since the efficiency for reformationof methane has to be raised. This means that the conventional typereformer has a drawback that the reforming catalyst is likelydeteriorated by the electrolyte. On the contrary, since the efficiencyfor reformation of methane is not an important factor in the system ofthe present invention, the reforming part 30a and the anode chamber 30bcan be provided separately, as shown in FIG. 8, and heat exchange may beeffected indirectuly therebetween. Therefore, the longevity of thereforming catalyst is prolonged.

The reformer shown in FIGS. 5 or 6 may be employed in place of thereformer 5 of FIG. 1. In addition, various aqueous solutions of otheramines or alkali metal salts or mixtures thereof may be employed as thecarbon dioxide gas-absorbing solution, in place of the aqueousdiethanolamine (DEA) solution.

As mentioned above, the anode exhaust gas exhausted from the anode ofthe fuel cell is transported to the carbon dioxide gas separator and thecarbon dioxide is separated from the exhaust gas. The residual gas notcontaining carbon dioxide gas is then fed into the anode of the fuelcell via the reformer, whereas the carbon dioxide gas is supplied intothe cathode of the fuel cell together with air. Accordingly, the fuelnot used in the fuel cell may be efficiently recirculated and completelyutilized for the cell reaction so that the power-producing efficiency isimproved. In addition, when methane is used as a fuel, the carbondioxide gas in the anode outlet gas may be separated and all the methanemay be resirculated to the reformer. This means that the fuelutilization efficiency does not drop even though the methane reformationis low. Accordingly, a design of the reformer can be simplified.Moreover, the cathode inlet temperature may be raised due to combustionby a burner so as to further improve the fuel cell characteristics. Inthis case, the anode exhaust gas containing less amount of carbondioxide is obtained so that an expensive catalyst combustion device isunnecessary.

I claim:
 1. An apparatus for producing electric power comprising:atleast one molten carbonate type fuel cell, the fuel cell including amolten carbonate-impregnated electrolyte tile sandwiched between ananode electrode and a cathode electrode both of which electrodes beingprovided with an anode chamber and a cathode chamber for feeding ananode gas and a cathode gas thereto, respectively; an anode gas feedline and an anode exhaust gas line connected with an inlet and an outletof the anode chamber of the fuel cell for introducing and exhausting theanode gas thereinto and therefrom, respectively; a cathode gas feed lineand a cathode exhaust line connected with an inlet and an outlet of thecathode chamber of the fuel cell for introducing and exhausting thecathode gas thereinto and therefrom, respectively; means for feeding afuel gas and a steam into the anode gas feed line; a reformer forreforming the fuel gas with a steam, as connected with the anode gasfeed line; a carbon dioxide gas separator for removing carbon dioxidegas from the anode exhaust gas in the anode exhaust gas line; acirculation line for recirculating into the reformer the anode exhaustgas from which carbon dioxide gas has been removed in the carbon dioxidegas separator; and means for feeding the carbon dioxide gas separated inthe carbon dioxide gas separator into the cathode gas feed line.
 2. Theapparatus as claimed in claim 11, wherein the carbon dioxide gasseparator includes an absorption column in which the anode exhaust gasis introduced from the anode exhaust gas line for conducting avapour-liquid contact of the anode exhaust gas with a carbondioxide-absorbing liquid and the thus contact-treated gas is dischargedto a circulation line, and a regeneration column connected with thecathode gas feed line in which the carbon dioxide-absorbed liquid fromthe absorption column is introduced and the liquid is stripped with airfed from the cathode gas feed line so as to release carbon dioxide gasfrom the liquid while the carbon dioxide gas-containing air is fed tothe cathode chamber and the liquid from which the carbon dioxide gas hasbeen stripped and released is recirculated to the said absorptioncolumn.
 3. The apparatus as claimed in claim 2, wherein the anodeexhaust gas line extending from the anode chamber to the absorptioncolumn is connected with condensing and separating means for isolatingthe steam from the anode exhaust gas.
 4. The apparatus as claimed inclaim 2, wherein the condensing and separating means is connected with asteam feed line through which the steam converted from a part of thecondensed and separated water by a heater is recirculated to an upperstream part of the anode gas feed line.
 5. The apparatus as claimed inclaim 1, wherein the anode exhaust gas or cathode exhaust gas isintroduced into the reformer as the heat source for maintaining thereforming temperature.
 6. An apparatus for producing electric powercomprising:at least one molten carbonate type fuel cell including amolten carbonate-impregnated electrolyte tile sandwiched between ananode electrode and a cathode electrode both of which electrodes beingprovided with an anode chamber and a cathode chamber for feeding ananode gas and a cathode gas thereto, respectively; an anode gas feedline and an anode exhaust gas line as connected with an inlet and anoutlet of the anode chamber of the fuel cell for introducing andexhausting the anode gas thereinto and therefrom, respectively; acathode gas feed line and a cathode exhaust line as connected with aninlet and an outlet of the cathode chamber of the fuel cell forintroducing and exhausting the cathode gas thereinto and therefromrespectively; means for feeding a fuel gas and a steam into the anodegas feed line; a reformer for reforming the fuel gas with a steam, asconnected with the anode gas feed line; a shift reactor connected withthe anode exhaust gas line for shifting the carbon monoxide gas andsteam in the anode exhaust gas to carbon dioxide gas and hydrogen; and acarbon dioxide gas separator includingan absorption column in which theanode exhaust gas from the said shift reactor is brought into contactwith a carbon dioxide-absorbing liquid by vapour-liquid contact and thethus contacted gas is recirculated to the said reformer, and aregeneration column connected with the cathode gas feed line in whichthe carbon dioxide-absorbed liquid from the absorption column isintroduced and the liquid is stripped with air as being fed from thecathode gas feed line so as to release carbon dioxide gas from theliquid while the carbon dioxide gas-containing air is fed to the cathodechamber and the liquid from which the carbon dioxide gas has beenstripped and released is recirculated to the said absorption column. 7.The apparatus as claimed in claim 6, wherein the anode exhaust gas linefrom the anode chamber to the absorption column is connected withcondensing and separating means for isolating the steam from the anodeexhaust gas.
 8. The apparatus as claimed in claim 7, wherein thecondensing and separating means is connected with a steam feed linethrough which the steam as converted from a part of the condensed andseparated water by a heater is resirculated to an upper stream part ofthe anode gas feed line.
 9. The apparatus as claimed in claim 6, whereinthe anode exhaust gas or cathode exhaust gas in introduced into thereformer as the heat source for maintaining the reforming temperature.10. An apparatus for producing electric power comprising:at least onemolten carbonate type fuel cell including a molten carbonate-impregnatedelectrolyte tile as sandwiched between an anode electrode and a cathodeelectrode both of which are provided with an anode chamber and a cathodechamber for feeding an anode gas and a cathode gas thereto,respectively; an anode gas feed line and an anode exhaust gas line asconnected with an inlet and an outlet of the anode chamber of the fuelcell for introducing and exhausting the anode gas thereinto andtherefrom, respectively; a cathode gas feed line and a cathode exhaustline as connected with an inlet and an outlet of the cathode chamber ofthe fuel cell for introducing and exhausting the cathode gas thereintoand therefrom, respectively; means for feeding a fuel gas and a steaminto the anode gas feed line; a reformer for reforming the fuel gas witha steam, as connected with the anode gas feed line; a carbon dioxide gasseparator includingan absorption column in which the anode exhaust gasfrom the anode exhaust gas line is brought into contact with a carbondioxide-absorbing liquid by vapour-liquid contact and the thus contactedgas is recirculated to the said reformer, and a regeneration columnconnected with the cathode gas feed line in which the carbondioxide-absorbed liquid from the said absorption column is introducedand the liquid is tripped with air as being fed from the cathode gasfeed line so as to release carbon dioxide gas from the liquid while theliquid from which the carbon dioxide gas has been stripped and releasedis recirculated to the said absorption column; and a combustion deviceconnected with the cathode gas feed line between the regeneration columnof the carbon dioxide gas separator and the cathode chamber in whichcombustion device a part of the anode exhaust gas coming from the saidabsorption column to the reformer is introduced and is combusted withthe air taken from the cathode gas feed line, so as to produce a cathodegas.
 11. The apparatus as claimed in claim 10, wherein the anode exhaustgas line extending from the anode chamber to the absorption column isconnected with condensing and separating menas for isolating the steamfrom the anode exhaust gas.
 12. The apparatus as claimed in claim 11,wherein the condensing and separating means is connected with a steamfeed line through which the steam as converted from a part of thecondensed and separated water by a heater is recirculated to an uppersteram part of the anode gas feed line.
 13. The apparatus as claimed inclaim 10, wherein the anode exhaust gas or cathode exhaust gas isintoroduced into the reformer as the heat source for maintaining thereforming temperature.
 14. An apparatus for producing electric powercomprising:a stack of internal reformation type molten carbonate fuelcells, each fuel cell including a molten carbonate-impregnatedelectrolyte tile which is sandwiched by an anode electrode and a cathodeelectrode both of which electrodes being provided with an anode chamberand a cathode chamber for feeding an anode gas and a cathode gasthereinto, respectively; a reformer provided between an arbitrary pairof anode chamber and cathode chamber for feeding a reformed gas into theanode chamber; a fuel gas and steam feed line for feeding a fuel gas anda steam into the reformer; an anode gas exhausting line connected withan outlet of the anode chamber for expelling the anode gas; a cathodegas feed line and a cathode exhaust gas line connected with an inlet andan outlet of the cathode chamber of the fule cell respectively forintroducing and discharging the cathode gas; and a carbon dioxide gasseparator which comprisesan absorption column in which the anode exhaustgas from the anode exhaust gas line is brought into contact with acarbon dioxide-absorbing liquid by vapour-liquid contact and the thuscontacted gas is recirculated into the fuel gas and steam feed line anda regeneration column connected with the cathode gas feed line in whichthe carbon dioxide-absorbed liquid from the said absorption column isintroduced and the liquid is stripped with air fed from the cathode gasfeed line so as to release carbon dioxide gas from the liquid while thecarbon dioxide gas-containing air is fed into the cathode chamber andthe liquid from which the carbon dioxide gas has been stripped andreleased is recirculated to the said absorption column.
 15. Theapparatus as claimed in claim 14, wherein condensing and separatingmeans for removing steam from the anode exhaust gas is connected withthe anode exhaust gas line as running from the anode chamber to theabsorption column.
 16. The apparatus as claimed in claim 15, wherein thecondensing and separating means is connected with a steam feed linethrough which the steam as converted from a part of the condensed andseparated water by a heater is recirculated to the fuel gas and steamfeed line.